Is a map type value possible?

[Ryan Kitchens]

I want something like a ChronicleMap<String, ConcurrentHashMap<String,String>>. I tried to mess around with ChronicleMapBuilder, but it seems what I am doing is not possible this way. Any ideas or different approach suggested?

    private static ChronicleMap<String, ConcurrentHashMap<String,String>> createChronicleMap() throws IOException {
        File dnmapfile = new File(dnmapfilename);

        ChronicleMapBuilder<String, ConcurrentHashMap<String, String>> builder = ChronicleMapBuilder.of(String.class, (Class<ConcurrentHashMap<String, String>>) (Class) ConcurrentHashMap.class);

        return builder.createPersistedTo(dnmapfile);
    }

I get the following error: "No field 'actualChunksPerSegment' found in class 'net.openhft.chronicle.map.VanillaChronicleMap"

Exception in thread "main" java.lang.AssertionError: java.lang.reflect.InvocationTargetException

    at net.openhft.chronicle.map.ChronicleMapBuilder.deserializeHeaderViaXStream(ChronicleMapBuilder.java:1356)

    at net.openhft.chronicle.map.ChronicleMapBuilder.createWithFile(ChronicleMapBuilder.java:1270)

    at net.openhft.chronicle.map.ChronicleMapBuilder.createPersistedTo(ChronicleMapBuilder.java:1241)

    at com.corp.group.DTracker.createChronicleMap(DTracker.java:53)

    at com.corp.group.DTracker.<init>(DTracker.java:40)

    at com.corp.group.LNotifier.main(LNotifier.java:27)

Caused by: java.lang.reflect.InvocationTargetException

    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)

    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

    at java.lang.reflect.Method.invoke(Method.java:497)

    at net.openhft.chronicle.map.ChronicleMapBuilder.deserializeHeaderViaXStream(ChronicleMapBuilder.java:1353)

    ... 5 more

Caused by: com.thoughtworks.xstream.converters.ConversionException: Could not call net.openhft.chronicle.map.VanillaChronicleMap.readObject() : No field 'actualChunksPerSegment' found in class 'net.openhft.chronicle.map.VanillaChronicleMap'

---- Debugging information ----

message             : Could not call net.openhft.chronicle.map.VanillaChronicleMap.readObject()

cause-exception     : com.thoughtworks.xstream.converters.reflection.MissingFieldException

cause-message       : No field 'actualChunksPerSegment' found in class 'net.openhft.chronicle.map.VanillaChronicleMap'

class               : net.openhft.chronicle.map.VanillaChronicleMap

required-type       : net.openhft.chronicle.map.VanillaChronicleMap

converter-type      : com.thoughtworks.xstream.converters.reflection.SerializableConverter

path                : /net.openhft.chronicle.map.VanillaChronicleMap/net.openhft.chronicle.map.VanillaChronicleMap/default/actualChunksPerSegment

line number         : 5

version             : 3.1.2-alpha-SNAPSHOT

-------------------------------

    at com.thoughtworks.xstream.core.util.SerializationMembers.callReadObject(SerializationMembers.java:133)

    at com.thoughtworks.xstream.converters.reflection.SerializableConverter.doUnmarshal(SerializableConverter.java:455)

    at com.thoughtworks.xstream.converters.reflection.AbstractReflectionConverter.unmarshal(AbstractReflectionConverter.java:263)

    at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:72)

    at com.thoughtworks.xstream.core.AbstractReferenceUnmarshaller.convert(AbstractReferenceUnmarshaller.java:65)

    at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:66)

    at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:50)

    at com.thoughtworks.xstream.core.TreeUnmarshaller.start(TreeUnmarshaller.java:134)

    at com.thoughtworks.xstream.core.AbstractTreeMarshallingStrategy.unmarshal(AbstractTreeMarshallingStrategy.java:32)

    at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:1206)

    at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:1190)

    at com.thoughtworks.xstream.XStream.fromXML(XStream.java:1070)

    ... 10 more

Caused by: com.thoughtworks.xstream.converters.reflection.MissingFieldException: No field 'actualChunksPerSegment' found in class 'net.openhft.chronicle.map.VanillaChronicleMap'

    at com.thoughtworks.xstream.converters.reflection.FieldDictionary.field(FieldDictionary.java:94)

    at com.thoughtworks.xstream.converters.reflection.PureJavaReflectionProvider.getFieldType(PureJavaReflectionProvider.java:159)

    at com.thoughtworks.xstream.converters.reflection.ReflectionProviderWrapper.getFieldType(ReflectionProviderWrapper.java:45)

    at com.thoughtworks.xstream.converters.reflection.SerializableConverter$2.defaultReadObject(SerializableConverter.java:411)

    at com.thoughtworks.xstream.core.util.CustomObjectInputStream.defaultReadObject(CustomObjectInputStream.java:116)

    at net.openhft.chronicle.map.VanillaChronicleMap.readObject(VanillaChronicleMap.java:192)

    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)

    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

    at java.lang.reflect.Method.invoke(Method.java:497)

    at com.thoughtworks.xstream.core.util.SerializationMembers.callReadObject(SerializationMembers.java:125)

    ... 21 more

[Rob Austin]

 Do you have a limited number of entries in the inner map. Under the covers, Chronicle works using fixed sizes. 

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[Roman Leventov]

Ryan,

1) seems you have serialized (created) a Chronicle Map of version 2.x..., then updated the dependency to the latest ChronicleMap, and then tried to deserialize. You should either revert dependency to 2.x or remove the map file and create a Map of version 3.x from scratch

2) Having ChronicleMap<K, ConcurrentMap<K2, V>> is pointless. all operations with the first-level key are synchronized on this key. Reads to the Map<K2, V> are already parallel. If you want to have _parallel writes_ to this secondary map, this is possible, but much more complex. You should access the first-level key like you are going to "read" the value (Map<K2, V>), and then update the raw bytes of the value via atomic operations.

[Roman Leventov]

I mean pointless to have ConcurrentMap<K2, V>. It's no different than just Map<K2, V>. If you want parallel writes to the secondary map, it shouldn't be even a map, if should be a complex bespoke data structure over raw bytes.

[Francesco Nigro]

Hi,
It's a "dirty" trick but maybe if the model Map<k1,Map<k2,v>> worth only to access a value V using K1 and then K2 , it could be possible to create a composite key:

interface CompositeKey{
K1 getKey1();
void setKey1(K1 key1);
K2 getKey2();
void setKey2(K2 key2);
}

And then create a ChronicleMap<CompositeKey,V>...

[Rob Austin]

Yes this would work, in certain circumstances, depending on your types. What type is K1 and K2.

Rob